The present disclosure generally relates to methods and devices for controlling and varying frictional force levels at an interface between the surfaces of two bodies.
Several devices or processes rely on the creation or elimination of a frictional force between opposing, contacting surfaces of two bodies to perform a specific function or operation. Exemplary devices having surfaces configured to produce or eliminate a frictional force include clutches, brakes (drum brakes, disc brakes, and the like), bearings, traction drives, devices that control fluid over or between surfaces, tires, mechanical seals, clamps, and the like. Many of these devices are either unable to control the frictional force level, or control the frictional force level by adjusting the speed of, or normal force exerted by, at least one of the contacting surfaces.
Existing devices utilize actuators and motors to change relative speeds of and/or normal forces exerted by at least one of the contacting surfaces. For example, brake actuators can change a normal force between brake pads to change frictional force levels. Current devices for changing frictional force levels, however, can be expensive due to the high costs of separate actuators or motors. Further, other operational or functional requirements may not permit actuators and motors to be utilized to control frictional force levels.
Accordingly, there remains a need for improved devices and methods for controlling the frictional force at the interface of two contacting bodies.